In recent years, in order to improve the fuel consumption, the development of a direct injection gasoline engine (downsizing engine) mounted with a supercharger, such as a turbo charger, etc., is being advanced at a quick pace. Because of direct injection, a soot (e.g., a particulate matter (PM) contained in an exhaust gas, etc.) is generated even in a gasoline engine likewise a diesel engine. For that reason, it is necessary to install a post-processing device of exhaust gas (in particular, a particulate filter or an exhaust gas cleaning device). However, it is known that a lubricating oil composition affects such a post-processing device of exhaust gas.
In the case of using a lubricating oil composition containing a metal-based detergent, there is a concern that in view of the matter that a metal component derived from the metal-based detergent deposits in the inside of a filter in the post-processing device of exhaust gas, clogging of the filter or worsening of catalytic activity is caused. For that reason, reduction of the ash content of the lubricating oil composition is demanded.
For example, PTL 1 discloses a lubricating oil composition for internal combustion engine, in which a calcium detergent, such as calcium phenate, etc., is blended such that a sulfuric acid ash content is 0.7 weight % or less.